1. Field of the Invention
The present disclosure relates to a substrate inspection apparatus that picks up an image of a substrate, such as a semiconductor wafer and an LCD substrate (a glass substrate for a liquid crystal display unit) so as to perform inspection of the substrate, and also relates to a method for operating the same.
2. Description of Related Art
In manufacturing of semiconductor devices, photolithographic processes, including a coating process that applies a resist solution to a semiconductor wafer (hereinafter referred to simply as “wafer”) to form a resist film, an exposure process that exposes the resist film with a predetermined pattern, and a developing process that develops the exposed resist film, are sequentially performed, so that a patterned resist film is formed on the wafer.
The wafer having experienced the photolithographic processes is loaded into a substrate inspection apparatus, which is disposed in a coating and developing system that performs the resist coating process and the developing process. Then, the surface of the wafer is imaged by a camera provided in the inspection apparatus, and the image of the wafer is displayed on an output screen. Based on the displayed image, there are performed inspection for inspecting whether or not the resist film is properly formed on the surface of the wafer, and inspection for inspecting whether or not the surface of the wafer has scratches and/or foreign matters adhered thereto.
Upon imaging, the wafer is illuminated by an illuminating unit provided in the substrate inspection apparatus. The illuminance of the illuminating unit gradually decreases by deterioration over time. When the wafer is imaged under a decreased illuminance, precision of inspection is reduced. Thus, periodic maintenance of the substrate inspection apparatus is performed. In some cases, an inspection wafer (i.e., a wafer exclusively for inspection or maintenance of the inspection apparatus) having thereon no film (e.g., a resist film) is loaded into the substrate inspection apparatus, and the illuminance of the illuminating unit is inspected based on an image obtained by imaging the inspection wafer. If it is judged that the illuminance of the illuminating unit is lower than a reference value, the illuminating unit is replaced or an amplification degree of a brightness signal is adjusted.
The inspection wafer is transferred from a dedicated carrier, which has been transferred to a loading port of the coating and developing system, to the inspection apparatus by means of a transfer mechanism of the coating and developing system. Transporting of the dedicated carrier to the loading port needs labor and time. Further, since transferring of product wafers by the transfer mechanism must be stopped while the inspection wafer is being transferred between the dedicated carrier and the inspection apparatus, the product wafers cannot be processed in the coating and developing system during the aforementioned operations for maintenance of the inspection apparatus. Thus, the maintenance work may decrease the throughput of the coating and developing system. On the other hand, if the frequency of the time-consuming, inconvenient maintenance work is lowered, a usable illuminating unit may be replaced uneconomically, or the inspection of the product wafers may be performed under the condition that the illuminance of the illuminating unit is lower than the reference value, resulting in low precision of the inspection.
JP2001-201431A (corresponding to U.S. Pat. No. 6,456,373 B1) describes an illuminating unit in which the intensity and the spectral distribution of a light emitted from a lamp are compared with references, and whether replacement of the lamp is required or not is alarmed based on the result. However, JP2001-201431A does not describe the above problem in connection with the inspection which is conducted with reference to the displayed image.